In a typical cellular network, also referred to as a wireless communication system, User Equipments (UEs), communicate via a Radio Access Network (RAN) to one or more core networks (CNs).
A user equipment is a mobile terminal by which a subscriber can access services offered by an operator's core network. The user equipments may be for example communication devices such as mobile telephones, cellular telephones, or laptops with wireless capability. The user equipments may be portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another mobile station or a server.
User equipments are enabled to communicate wirelessly in the cellular network. The communication may be performed e.g. between two user equipments, between a user equipment and a regular telephone and/or between the user equipment and a server via the radio access network and possibly one or more core networks, comprised within the cellular network.
The cellular network covers a geographical area which is divided into cell areas. Each cell area is served by a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also on cell size.
A cell is a geographical area where radio coverage is provided by the base station at a base station site on a specific radio frequency band using a specific radio access technology. One base station, situated on the base station site, may serve one or several cells covering non-overlapping, partly overlapping or completely overlapping geographical areas. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations.
In some radio access networks, several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunications System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Spécial Mobile).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or eNBs, may be directly connected to one or more core networks.
UMTS is a third generation, 3G, mobile communication system, which evolved from the second generation, 2G, mobile communication system GSM, and which is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipments. The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
According to 3GPP/GERAN, a user equipment has a multi-slot class, which determines the maximum transfer rate in the uplink and downlink direction. GERAN is an abbreviation for GSM EDGE Radio Access Network. EDGE is further an abbreviation for Enhanced Data rates for GSM Evolution.
In the context of this disclosure, a base station as described above will be referred to as a base station or a Radio Base Station (RBS). A user equipment as described above, will in this disclosure be referred to as a user equipment or a UE.
The expression DownLink (DL) will be used for the transmission path from the base station to the user equipment. The expression UpLink (UL) will be used for the transmission path in the opposite direction i.e. from the user equipment to the base station.
Cellular network operators have considerable effort in planning, configuring, optimizing, and maintaining their wireless access networks. These efforts may consume a great part of their Operational Expenditures (OPEX).
One important E-UTRAN requirement from the operators' side is hence a reduction in the cost for deployment, configuration, and optimization phases for the wireless access system. This may involve tasks for operating the cellular network, e.g., planning and verification. Today, operators resort to planning tools to dimension and plan their cellular networks according to a specific business strategy. The approach based on planning tools and prediction is, however, not fully accurate. Reasons for the inaccuracies are imperfections in the used geographic data, simplifications and approximations in the applied propagation models, and changes in the environment, e.g., construction and/or demolition or seasonal effects, i.e. foliage changes. Furthermore, changes in the traffic distribution and user profiles may lead to inaccurate prediction results.
The above mentioned shortcomings force operators to continuously optimize their cellular networks using measurements and statistics, and to perform drive test or walk tests. Drive test and walk tests provide a picture of the end user perception in the field and enables the operator to identify locations causing poor performance and their corresponding cause, e.g. incorrect tilt or handover settings. Drive test and walk tests, however, may only cover a limited part of the cellular network due to access restrictions and the cost and time involved. Further, only a snapshot in time of the conditions in the field is captured.
Hence, for network management purposes, a problem is that only a limited part of the cellular network may be analyzed.
Planning and verification for managing the cellular network may also be based on so called “measurement reports” from user equipments. In such reports the observed service quality may be reported to a network management unit within the cellular network. The triggering of the measurement report may either be periodic, event-triggered or event triggered periodic reporting. Periodic reporting may be initiated when the event occurs. Example of such events may be that an alternative cell is received at higher power levels compared to the serving cell, radio link failure, etc. Optionally, if available, these measurement reports may be tagged with an estimated mobile position. The standardization of such measurement reports is currently being carried out in 3GPP as Minimization of Drive-Tests (MDT).
However, the measurement reports are limited to reporting service quality measurements that are configured via the Radio Resource Control (RRC) measurement control and reporting procedures, such as Reference Symbol Received Power (RSRP) and Reference Symbol Received Quality (RSRQ), which are intended for mobility and other longer time scale radio resource mechanisms.